fix(opfs): add auto OPFS file registration & update dropFiles method

[e1arikawa]

Summary

• Auto File Registration:
  When AsyncDuckDB#runQuery or startPendingQuery includes an opfs:// file path, the function automatically calls AsyncDuckDB#registerFileHandler.

  • Enabled by setting autoFileRegistration: true in the DuckDBConfig passed to AsyncDuckDB#open.

• dropFiles Method Updates:

  • No arguments: Drops all registered files.
  • With arguments: Drops only the specified file(s).

Rationale

• This feature simplifies the usage of OPFS by removing the need to manually register file handlers in most cases.
• Updating the dropFiles method improves flexibility and convenience for file management.

Testing

• Verified that autoFileRegistration: true triggers automatic file registration correctly.
• Confirmed that dropFiles() without arguments removes all registered files, and dropFiles("someFile") removes only the specified file.

Impact

• Users who do not enable autoFileRegistration will not see any change in behavior regarding file registration.
• Since dropFiles originally did not accept arguments, existing calls using no arguments remain unaffected.
  However, if any code previously passed arguments (intentionally or unintentionally), the behavior might now differ because those arguments will be processed instead of ignored.
• If your code relies on the old behavior, please review these changes and update as needed.

[carlopi]

Problem I see with that is that's not obvious which files might/will be read for a given query / needs preparing.

Example:

COPY (SELECT 32) TO 'opfs://file.csv';
--- opfs://file.csv is written

COPY (SELECT 42) TO 'opfs://file.csv';
---  opfs://tmp_file.csv AND opfs://file.csv are written

I will write down later what seems a better solution (to me)